TWI683403B - Method of producing power module substrate with heat sink - Google Patents

Abstract

A method of producing a power module substrate with a heat sink includes performing solid-phase diffusion bonding a metal layer and a heat sink. Any one of an aluminum material composing a bonding surface of the metal layer and an aluminum material composing a bonding surface of the heat sink is a high purity aluminum material containing high purity aluminum. The other thereof is a low purity aluminum material containing low purity aluminum. The difference between the concentration of elements other than Al in the high purity aluminum material and in the low purity aluminum material is 1 atom% or more.

Description

Method for manufacturing substrate for power module with heat sink

The present invention relates to a method for manufacturing a substrate for a power module with a heat sink, which includes an insulating layer, a circuit layer formed on one side of the insulating layer, a metal layer formed on the other side of the insulating layer, and A heat sink arranged on the surface of the metal layer opposite to the insulating layer.

This application claims priority based on Japanese Patent Application No. 2015-069860 filed in Japan on March 30, 2015, and the contents are used here.

In general, the amount of heat generated by power semiconductor elements for controlling large power used in wind power generation, electric vehicles, hybrid vehicles, etc. is large. Therefore, the power semiconductor element is mounted so the substrate, for example, widely used conventional power module substrate, the power module substrate provided with a line of AlN (aluminum nitride), Al ₂ O ₃ (alumina), etc. The formed ceramic substrate, the circuit layer formed on one side of the ceramic substrate, and the metal layer formed on the other side of the ceramic substrate.

In addition, a heat-dissipating fin-attached substrate for a power module in which a heat sink is bonded to a metal layer side to efficiently diffuse heat generated by mounted semiconductor elements and the like is provided.

For example, Patent Document 1 discloses a power module substrate with a heat sink. The circuit layer and the metal layer of the power module substrate are made of aluminum or aluminum alloy, and the heat sink is made of aluminum or aluminum. It is composed of alloy, and the metal layer and the heat sink are joined together by welding or brazing.

In addition, Patent Document 2 discloses a substrate for a power module with a heat sink. The circuit layer and the metal layer made of aluminum are formed on one side and the other side of the ceramic substrate. A copper plate is arranged between the sheets, and the metal layer and the copper plate, and the copper plate and the heat sink are welded separately.

Furthermore, Patent Document 3 discloses that the circuit layer and the metal layer of the substrate for the power module are composed of aluminum or aluminum alloy, and the heat sink is composed of aluminum or aluminum alloy. In the substrate, a bonding material made of copper or a copper alloy is interposed between the metal layer and the heat sink, and the metal layer and the joint material and the joint material and the heat sink are separately solid-phase diffusion bonded.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2008-016813

[Patent Document 2] Japanese Patent Laid-Open No. 2007-250638

[Patent Document 3] Japanese Unexamined Patent Publication No. 2014-060215

In addition, the recent development of high output of power semiconductor devices and the like has become a severe thermal cycle on the substrate of the power module with its heat sink attached, and it is more important than ever to have an excellent bonding reliability for thermal cycles. Substrate for power module with heat sink.

Here, in the substrate for a power module with a heat sink described in Patent Document 1, when a metal layer and a heat sink are soldered, there may be cracks at the solder joints when the heat cycle load occurs and the joints The problem of reduced rates.

In addition, when the metal layer and the heat sink are brazed, there is a possibility that the ceramic substrate may crack due to thermal cycling load.

Furthermore, in a heat sink with a complicated structure in which a cooling medium flow path is formed, it is sometimes made of an aluminum casting alloy with a low solidus temperature, but in such a heat sink, it is used It is difficult to join brazing materials.

In addition, in the substrate for a power module with a heat sink described in Patent Document 2, since the metal layer and the copper plate, and the copper plate and the heat sink are soldered separately, they still occur at the place of the solder during the heat cycle load The problem of cracking and lowering the bonding rate.

Furthermore, in the substrate for a power module with a heat sink shown in Patent Document 3, a bonding material composed of copper or a copper alloy is interposed between the metal layer and the heat sink, and the metal layer is bonded to the bonding material and Material and heat sink Solid phase diffusion bonding is performed separately, and an intermetallic compound is formed at the bonding interface between the metal layer and the heat sink. Since this intermetallic compound is hard and brittle, there is a possibility that cracks or the like may occur when the heat cycle is loaded.

The present invention has been completed in view of the foregoing circumstances, and its object is to provide a method for manufacturing a substrate for a power module with a heat sink that can manufacture a substrate for a power module with a heat sink, the power supply with a heat sink The module substrate system can suppress the occurrence of cracks at the bonding interface even under load thermal cycling.

In order to solve such a problem and achieve the aforementioned object, the manufacturing method of a substrate for a power module with a heat sink in the same form of the present invention is provided with an insulating layer, a circuit layer formed on one side of the insulating layer, formed on the aforementioned The manufacturing method of the metal layer on the other surface of the insulating layer and the heat sink-attached power module substrate provided on the surface of the metal layer opposite to the insulating layer is characterized in that the metal layer The bonding surface with the heat sink and the bonding surface with the metal layer of the heat sink are made of aluminum material made of aluminum or aluminum alloy, the aluminum material constituting the bonding surface of the metal layer and the heat sink One of the aluminum materials on the joining surface is a high-purity aluminum material with high purity aluminum, and the other is a low-purity aluminum material with low purity aluminum. The high-purity aluminum material and the low-purity aluminum material other than Al The concentration difference of the element is set to 1 atomic% or more, and the metal layer and the heat sink are subjected to solid phase diffusion bonding.

Manufacturing of a substrate for a power module with a heat sink constituted here In the manufacturing method, the bonding surface of the metal layer with the heat sink and the bonding surface of the heat sink with the metal layer are made of aluminum material made of aluminum or aluminum alloy, and the metal layer and the heat sink Perform solid phase diffusion bonding. Generally, when aluminum materials are solid-phase diffused with each other, since the self-diffusion rate of aluminum is slow, it takes a long time to obtain a strong solid-phase diffusion bonding system, which is not industrially feasible.

Here, in the present invention, either one of the aluminum material constituting the bonding surface of the metal layer and the aluminum material constituting the bonding surface of the heat sink is a high-purity aluminum material with high purity of aluminum, and the other is aluminum The low-purity aluminum material with low purity has a difference in concentration of elements other than Al between the high-purity aluminum material and the low-purity aluminum material to 1 atomic% or more. The side diffuses toward the high-purity aluminum material side, and promotes the self-diffusion of aluminum, so that it is possible to reliably perform solid-phase diffusion bonding of the metal layer and the heat sink in a short time.

In addition, since the heat sink and the metal layer are diffusion-bonded in a solid phase in this way, even in the case of a load thermal cycle, there is no doubt that a crack or the like is generated at the bonding interface, and excellent bonding reliability for thermal cycle can be obtained A substrate for power modules with heat sinks.

In the manufacturing method of a substrate for a power module with a heat sink in the same state of the present invention, it is preferable that the high-purity aluminum material and the low-purity aluminum material contain Si, Cu, Mn, Fe, Mg, Zn , Ti and Cr selected one or two or more elements as elements other than Al, and the total amount of elements other than Al in the high-purity aluminum material and the elements other than Al in the low-purity aluminum material Contains elements The total difference is at least 1 atom%.

In this case, the elements of Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr are excellent in the effect of promoting the self-diffusion of aluminum, so it becomes possible to combine the metal layer and the heat sink composed of aluminum materials. Solid phase diffusion bonding is performed reliably in a short time.

In addition, in the manufacturing method of a substrate for a power module with a heat sink in the same state of the present invention, it is preferable that the total amount of the low-purity aluminum material contains 1 atomic% or more of Si, Cu, Mn, Fe, and Mg , Zn, Ti and Cr selected one or more elements, and the content of Si is 15 atomic% or less, the content of Cu is 10 atomic% or less, the content of Mn is 2 atomic% or less, the content of Fe is 1 atomic% or less, Mg content is 5 atomic% or less, Zn content is 10 atomic% or less, Ti content is 1 atomic% or less, and Cr content is 1 atomic% or less.

In this case, since the low-purity aluminum material with a low purity contains 1 atomic% or more in total, one or more elements selected from Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr, so By diffusing these elements toward the side of the high-purity aluminum material to promote the self-diffusion of aluminum, it becomes possible to reliably perform solid-phase diffusion bonding of the metal layer and the heat sink in a short time.

On the other hand, it is limited to: the content of Si is 15 atomic% or less, the content of Cu is 10 atomic% or less, the content of Mn is 2 atomic% or less, the content of Fe is 1 atomic% or less, and the content of Mg is 5 At% or less, Zn content is 10% or less, Ti content is 1% or less, and Cr content is 1% or less, so these elements can be It is possible to reliably manufacture a substrate for a power module with a heat sink with excellent bonding reliability to a heat sink by suppressing the bonding interface to be harder than necessary.

Furthermore, in the manufacturing method of a substrate for a power module with a heat sink in the same form of the present invention, it is preferable to have the following structure: by laminating the above-mentioned generic layer and the above-mentioned heat sink to facilitate lamination The direction load is 0.3MPa or more and 3.0MPa or less, and it is maintained at a holding temperature of 90% or more of the solidus temperature (K) of the low-purity aluminum material and the solidus temperature of the low-purity aluminum material. For more than hours, the metal layer and the heat sink are subjected to solid phase diffusion bonding.

In this case, it is in a state where the load in the lamination direction is 0.3 MPa or more and 3.0 MPa or less, and the low-purity aluminum is not more than 90% of the solidus temperature (K) of the low-purity aluminum material. The solid-phase diffusion bonding conditions of the material are maintained at the solidus temperature for more than 1 hour. Therefore, the diffusion movement of aluminum can be promoted, and the metal layer and the heat sink can be reliably bonded.

According to the present invention, it is possible to provide a method for manufacturing a substrate for a power module with a heat sink that can manufacture a substrate for a power module with a heat sink, the substrate for a power module with a heat sink is even under load The thermal cycle can also suppress the occurrence of cracks at the joint interface.

1, 101, 201 ‧‧‧ power module

10, 110, 210‧‧‧ substrate for power module

11‧‧‧Ceramic substrate

12, 112, 212‧‧‧ circuit layer

13, 113, 213‧‧‧ metal layer

30, 130, 230 ‧‧‧ substrate for power module with heat sink

31, 131, 231‧‧‧ heat sink

[Figure 1] This is a schematic explanatory diagram of a heat sink-attached power module substrate and power module according to an embodiment of the present invention.

[Figure 2] This is a diagram showing the observation results and analysis results of the bonding interface between the metal layer of the power module substrate with heat sink and the heat sink.

[Figure 3] is a flowchart showing a method for manufacturing a power module substrate with a heat sink and a power module according to an embodiment of the present invention.

[FIG. 4] It is explanatory drawing which shows the manufacturing method of the board|substrate for power supply modules with a heat sink which concerns on embodiment of this invention.

[FIG. 5] This is a schematic explanatory diagram of a heat sink-attached power module substrate and power module according to another embodiment of the present invention.

[Figure 6] This is a schematic explanatory diagram of a power-supply module substrate with a heat sink and a power module according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

FIG. 1 shows a heat sink-attached power module substrate 30 and a power module 1 according to an embodiment of the present invention.

This power module 1 is provided with a substrate 30 for a power module with a heat sink, and one side of the substrate 30 for a power module with a heat sink attached via the solder layer 2 (in FIG. 1 is The above) of the semiconductor element 3.

Here, the solder layer 2 system is, for example, a Sn-Ag system, Sn-In system, or Sn-Ag-Cu system solder material.

In addition, the heat sink-attached power module substrate 30 of the present embodiment includes the power module substrate 10 and the heat sink 31 bonded to the power module substrate 10.

The power supply module substrate 10 includes a ceramic substrate 11, a circuit layer 12 disposed on one side (upper surface in FIG. 1) of the ceramic substrate 11, and the other surface disposed on the ceramic substrate 11 ( In the first figure, the metal layer 13 below).

The ceramic substrate 11 prevents the electrical connection between the circuit layer 12 and the metal layer 13, and in this embodiment is composed of AlN (aluminum nitride) with high insulation. Here, the thickness of the ceramic substrate 11 is set within a range of 0.2 mm or more and 1.5 mm or less, and in the present embodiment, it is set to 0.635 mm.

The circuit layer 12 is formed by joining an aluminum plate 22 made of aluminum or aluminum alloy to one side of the ceramic substrate 11 as shown in FIG. 4. In this embodiment, as the aluminum plate 22 constituting the circuit layer 12, a rolled plate of 2N aluminum having a purity of 99 mass% or more is used. A circuit pattern is formed on the circuit layer 12, and one surface (the upper surface in the first drawing) is a mounting surface on which the semiconductor element 3 is mounted. Here, the thickness of the circuit layer 12 (aluminum plate 22) is set within a range of 0.1 mm or more and 1.0 mm or less, and in this embodiment, it is set to 0.6 mm.

As shown in FIG. 4, the metal layer 13 is formed by bonding an aluminum plate 23 made of aluminum or aluminum alloy to the other surface of the ceramic substrate 11. In this embodiment, as the aluminum plate 23 constituting the metal layer 13, a rolled plate of 4N aluminum having a purity of 99.99 mass% or more is used. Here, the metal layer The thickness of 13 (aluminum plate 23) is set within a range of 0.1 mm or more and 6.0 mm or less, and in the present embodiment, it is set to 2.0 mm.

The heat sink 31 is used for diffusing the heat of the power module substrate 10 side, and in this embodiment, as shown in FIG. 1, a flow path 32 is provided for the cooling medium to circulate.

The heat sink 31 is such that the concentration difference of the elements other than Al constituting the aluminum layer of the metal layer 13 (in this embodiment, 4N aluminum with a purity of 99.99 mass% or more) and the aluminum alloy constituting the heat sink 31 becomes 1 atomic% Made of the above materials.

More preferably, one or more elements selected from Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr are included as elements other than Al.

Even more preferably, it contains 1 atomic% or more of one or more elements selected from Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr as elements other than Al, and the content of Si is 15 atomic% or less, Cu content 10 atomic% or less, Mn content 2 atomic% or less, Fe content 1 atomic% or less, Mg content 5 atomic% or less, Zn content 10 atomic% or less, The content of Ti is 1 atomic% or less and the content of Cr is 1 atomic% or less.

In the present embodiment, the heat sink 31 is composed of the ADC12 of the aluminum alloy for die casting specified in JIS H 2118:2006. In addition, the ADC12 series includes aluminum alloys in which Cu is 1.5 mass% or more and 3.5 mass% or less, and Si is 9.6 mass% or more and 12.0 mass% or less.

Furthermore, in the substrate 30 for a power module with a heat sink of this embodiment, the metal layer 13 and the heat sink 31 are diffused by solid phase Joined. That is, in this embodiment, since the metal layer 13 is composed of 4N aluminum with a purity of 99.99 mass% or more, and the heat sink 31 is composed of the ADC 12 of aluminum alloy for die casting, the metal layer 13 and the heat dissipation The sheet 31 has different purity of aluminum. The metal layer 13 is made of high-purity aluminum material, and the heat sink 31 is made of low-purity aluminum material.

Here, JXA-8530F manufactured by JEOL Ltd. is used for the bonding interface between the metal layer 13 and the heat sink 31, and the observation results of the images obtained by SEM and EPMA are shown in FIGS. 2(a) to (c). It can be confirmed from FIGS. 2(a) to (c) that the added elements (Cu, Si) included in the heat sink 31 diffuse to the metal layer 13 side. In addition, the diffusion depth from the junction interface to the metal layer 13 side is 10 μm or more for Cu and 45 μm or more for Si. In addition, Cu may be 25 μm or more, and Si may be 45 μm or more.

Next, the method of manufacturing the heat sink-attached power module substrate 30 of the present embodiment described above will be described with reference to FIGS. 3 and 4.

(Aluminum plate joining step S01)

First, as shown in FIG. 4, the aluminum plate 22 serving as the circuit layer 12 and the aluminum plate 23 serving as the metal layer 13 are bonded to the ceramic substrate 11. In this embodiment, the aluminum plate 22 made of a 2N aluminum rolled plate, the aluminum plate 23 made of a 4N aluminum rolled plate, and the ceramic substrate 11 made of AlN are each made of an Al-Si brazing material 24 Join.

In this aluminum plate bonding step S01, first, on the ceramic base One side and the other side of the plate 11 are respectively laminated with an aluminum plate 22 and an aluminum plate 23 via an Al-Si brazing material 24 (aluminum plate lamination step S11).

Next, by loading the laminated ceramic substrate 11, the aluminum plate 22, and the aluminum plate 23 in the lamination direction with a load of 0.1 MPa or more and 3.5 MPa or less, it is placed in a heating furnace in a vacuum or argon environment at 600°C. Above and below 650°C for 0.5 hours or more and 3 hours or less, a molten metal region is formed between the ceramic substrate 11 and the aluminum plate 22 and the aluminum plate 23 (heating step S12).

Thereafter, the molten metal region is solidified by cooling (solidification step S13). In this way, the aluminum plate 22 and the ceramic substrate 11 and the aluminum plate 23 are joined to form the circuit layer 12 and the metal layer 13. With this, the power module substrate 10 of this embodiment is manufactured.

(Sink bonding step S02)

Next, the heat sink 31 is bonded to the other surface of the metal layer 13 of the power module substrate 10 (the surface opposite to the bonding surface of the ceramic substrate 11 ).

In this heat sink bonding step S02, first, as shown in FIG. 4, the heat sink 31 is laminated on the other surface side of the power module substrate 10 (heat sink lamination step S21).

In this state, the laminate of the power module substrate 10 and the heat sink 31 is loaded into the vacuum heating furnace in a state where the load in the lamination direction is 0.3 MPa or more and 3.0 MPa or less.

Next, the temperature is kept at 90% or more of the solidus temperature (K) of the low-purity aluminum material and at a temperature that does not reach the solidus temperature of the low-purity aluminum material for 1 hour. The solid phase diffusion bonding is performed as described above (solid phase diffusion bonding step S22). In addition, 90% of the solidus temperature (K) of the low-purity aluminum material refers to the temperature of 90% when the solidus temperature of the low-purity aluminum is expressed in absolute temperature. In this embodiment, ADC12 is a low-purity aluminum material, and its solidus temperature is 788K (515°C). Therefore, the heating temperature is 90% of the solidus temperature, that is, more than 709.2K (436.2°C), and the solidus temperature is not reached, that is, less than 788K (515°C).

In the present embodiment, the bonding surface of the metal layer 13 and the fins 31 is solid-phase diffusion bonding after the damage of the surface is removed in advance to become smooth. In addition, the surface roughness of the joint surface of the metal layer 13 and the heat sink 31 at this time is set to a range of 0.5 μm or less in terms of arithmetic average roughness Ra (JIS B 0601 (1994)).

In this way, the heat sink-attached power module substrate 30 of this embodiment is manufactured.

(Semiconductor element bonding step S03)

Next, the semiconductor element 3 is bonded to one side of the circuit layer 12 of the power module substrate 10 by soldering.

Through the above steps, the power module 1 shown in FIG. 1 is manufactured.

According to the manufacturing method of the substrate 30 for a power module with a heat sink of the present embodiment configured as above, since the aluminum material constituting the metal layer 13 is 4N aluminum having a purity of 99.99 mass% or more, the aluminum constituting the heat sink 31 The material is composed of ADC12 (Cu: 1.5mass% or more, 3.5mass% or less, Si: 9.6mass% or more, 12.0mass% or less), because During solid phase diffusion bonding, Cu and Si of the heat sink 31 diffuse toward the metal layer 13 to promote the self-diffusion of aluminum. This makes it possible to reliably perform solid-phase diffusion bonding of the metal layer and the heat sink in a short time.

Next, in this embodiment, since the metal layer 13 and the heat sink 31 both made of aluminum are solid-phase diffusion bonded, as shown in FIG. 2, at the junction interface of the heat sink 31 and the metal layer 13 No out of phase.

Therefore, even in the case of a thermal cycle under load, there is no possibility of cracks at the bonding interface, and the substrate 30 for a power module with a heat sink with excellent bonding reliability for thermal cycles can be manufactured.

Moreover, in this embodiment, the aluminum material constituting the heat sink 31 is composed of ADC12 (Cu: 1.5 mass% or more, 3.5 mass% or less, Si: 9.6 mass% or more, 12.0 mass% or less), such Cu and Si Since the effect of promoting the self-diffusion of aluminum is excellent, it becomes possible to reliably perform solid-phase diffusion bonding of the metal layer 13 and the heat sink 31 each composed of an aluminum material in a short time.

Furthermore, in the aluminum material constituting the heat sink 31, the Si content is 12.0 mass% or less (11.6 atomic% or less (converted value)), and the Cu content is 3.5 mass% or less (1.5 atomic% or less (converted value)) Therefore, by these elements, it is possible to suppress the bonding interface to be harder than necessary, and it is possible to reliably manufacture a substrate for a power module with a heat sink, which is excellent in bonding reliability for thermal cycles.

Furthermore, since the metal layer 13 and the heat sink 31 are laminated, the load in the lamination direction is 0.3 MPa or more and 3.0 MPa or less Loaded state, and maintained at a temperature above 90% of the solidus temperature (K) of the low-purity aluminum material and less than the holding temperature of the solidus temperature of the low-purity aluminum material for more than 1 hour, and the metal layer 13 and the heat sink 31 performs solid-phase diffusion bonding, so that the diffusion movement of aluminum can be promoted, and the metal layer 13 and the heat sink 31 can be reliably bonded.

When the load is 0.3 MPa or more, the contact area at the initial stage of bonding is sufficiently ensured, and the metal layer 13 and the heat sink 31 can be bonded well. In addition, when the load is 3.0 MPa or less, deformation of the metal layer 13 or the heat sink 31 can be suppressed.

When the holding temperature is 90% or more of the solidus temperature (K) of the low-purity aluminum material, a sufficient diffusion rate can be ensured, and the metal layer 13 and the heat sink 31 can be well bonded. When the holding temperature is less than the solidus temperature of the low-purity aluminum material, since no liquid phase occurs and deformation of the metal layer 13 or the heat sink 31 can be suppressed, the metal layer 13 and the heat sink 31 can be suppressed Solid-phase diffusion bonding is surely performed.

In the case where the holding time is 1 hour or more, the solid phase diffusion can be sufficiently performed, and the metal layer 13 and the heat sink 31 can be bonded well.

Furthermore, in this embodiment, the damage of the bonding surface of the metal layer 13 and the heat sink 31 before bonding is removed, and the surface roughness is set to an arithmetic average roughness Ra (JIS B 0601 (1994)) Is within the range of 0.5 μm or less, so that the metal layer 13 and the heat sink 31 are reliably in contact, and the diffusion movement of aluminum atoms and the added elements (Cu, Si) of the heat sink 31 can be promoted, and the metal layer 13 and The heat sink 31 is surely joined.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.

For example, the material of the metal layer and the heat sink is not limited by this embodiment, as long as either one of the aluminum material constituting the bonding surface of the metal layer and the aluminum material constituting the bonding surface of the heat sink is high purity aluminum with high purity The other material is a low-purity aluminum material with low purity of aluminum, and the difference in concentration of elements other than Al between the high-purity aluminum material and the low-purity aluminum material may be 1 atomic% or more.

Specifically, in the present embodiment, although the metal layer is described as composed of 4N aluminum with a purity of 99.99 mass%, it is not limited to this, and may be composed of other pure aluminum or aluminum alloys . For example, 2N aluminum with a purity of 99 mass% or higher such as A1050 or A1085 can also be used. In this case, since the initial impurity concentration of the metal layer is high, the growth of crystal grains at the bonding temperature is suppressed, and the diffusion of grain boundaries can be expected. Therefore, it becomes possible to promote the diffusion movement of the element contained from the heat sink side.

In addition, in this embodiment, although the heat sink is described as being composed of ADC12, it is not limited to this, and may be composed of other pure aluminum or aluminum alloys such as A3003 or A6063.

Alternatively, the heat sink side may be made of high-purity aluminum material, and the metal layer side may be made of low-purity aluminum material.

In this embodiment, although the entire metal layer is made of aluminum or aluminum alloy, it is not limited to this. For example, the fifth As shown in the figure, as long as the bonding surface between the metal layer and the heat sink is made of aluminum or aluminum alloy. In the power module substrate 130 and power module 101 with a heat sink shown in FIG. 5, the metal layer 113 is a structure in which a copper layer 113A and an aluminum layer 113B are laminated, and the ceramic substrate 11 and copper The layer 113A is bonded, and the aluminum layer 113B and the heat sink 131 are solid-phase diffusion bonded. In addition, in FIG. 5, the circuit layer 112 also has a structure in which a copper layer 112A and an aluminum layer 112B are laminated, and the semiconductor element 3 is joined to the aluminum layer 112B via the solder layer 2.

Similarly, in this embodiment, although the whole heat sink is made of aluminum or aluminum alloy, it is not limited to this. For example, as shown in FIG. 6, as long as the bonding surface between the heat sink and the metal layer It may be composed of aluminum or aluminum alloy. In the substrate 230 for a power module with a heat sink and the power module 201 shown in FIG. 6 here, the heat sink 231 is composed of an aluminum layer 231B composed of aluminum or an aluminum alloy laminated with copper or copper The structure of the heat sink body 231A made of an alloy solid-phase diffusion-bonds the metal layer 213 and the aluminum layer 231B (heat sink 231).

In this embodiment, although the aluminum plate constituting the circuit layer is described as 2N aluminum with a purity of 99 mass%, it is not limited to this, and may be pure aluminum with a purity of 99.99 mass% or more. Or other pure aluminum or aluminum alloy.

Furthermore, in the present invention, the structure of the circuit layer is not limited, and design changes can be made as appropriate. For example, it may be composed of copper or a copper alloy, or as shown in FIG. 5 with the substrate 130 for a power module with a heat sink and the power module 101, the circuit layer 112 is a laminate of a copper layer 112A and an aluminum layer 112B Construct Made.

Furthermore, in the present embodiment, although the aluminum plate and the ceramic substrate that are the circuit layer and the metal layer are joined by using an Al-Si brazing material, it is not limited to this, and a transition liquid phase junction may also be used. Legal (Transient Liquid Phase Bonding), casting method, metal bonding method, etc. for bonding.

In this embodiment, although the insulating layer is described as a ceramic substrate made of AlN, it is not limited to this, and other ceramics such as Si ₃ N ₄ or Al ₂ O ₃ may be used. Substrate.

In addition, the thicknesses of the insulating layer, the circuit layer, the metal layer, and the heat sink are also limited by this embodiment, and design changes can be made as appropriate.

[Examples]

A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.

According to the procedure described in the flowchart of FIG. 3, the heat sink-attached power module substrates of the present invention and the comparative examples were produced.

The ceramic substrate is made of AlN, and has a size of 40 mm×40 mm and a thickness of 0.635 mm.

The circuit layer is formed by bonding a 2N aluminum rolled plate (37 mm×37 mm, thickness 0.6 mm) with a purity of 99 mass% or more to a ceramic substrate using an Al-7.5 mass% Si brazing material.

The metal layer is made of Al-7.5mass%Si brazing material by using a rolled plate (37mm×37mm, thickness 0.6mm) composed of the aluminum materials shown in Table 1. It is expected to be formed by bonding to a ceramic substrate.

The heat sink is made of the materials described in Table 2, and is 50mm×50mm and 5mm thick.

The solid phase diffusion bonding of the metal layer and the heat sink is carried out under the conditions shown in Table 3.

Furthermore, the following heat sink-attached power module substrates were produced as Conventional Examples 1 to 3.

By using a 2N aluminum rolled plate (37mm × 37mm, thickness 0.6mm) as a circuit layer and a ceramic substrate (40mm × 40mm, thickness 0.635mm) made of AlN and a 4N aluminum rolled plate (37mm) as a metal layer ×37mm, thickness 0.6mm), laminated via Al-7.5mass%Si brazing material, placed in a vacuum heating furnace with a pressure of 5kgf/cm ² in the lamination direction, and heated at 650°C for 30 The bonding is performed in minutes to produce a substrate for a power module.

In addition, in the conventional example 1, the substrate for the power module and the heat sink after the Ni plating (rolled plate of A6063, 50 mm×50 mm, thickness 5 mm) were joined via Sn-Ag-Cu solder.

In the conventional example 2, the substrate for the power module and the heat sink (the calendered plate of A6063, 50 mm×50 mm, thickness 5 mm) were joined via an Al-10mass%Si brazing material.

In the conventional example 3, the substrate for the power module and the heat sink (the calender plate of A6063, 50 mm×50 mm, thickness 5 mm) were solid-phase diffusion bonded via Cu foil (thickness: 200 μm).

(Diffusion distance with elements)

A cross-sectional observation near the junction interface of the obtained heat sink and metal layer of the present invention example was carried out, and the diffusion distance of elements other than Al from the low-purity aluminum material side to the high-purity aluminum material side was measured. The evaluation results are shown in Table 4.

The diffusion distance of the element is measured by the line analysis by EPMA (JXA-8530F manufactured by JEOL Ltd.) from the junction interface of the low-purity aluminum material and the high-purity aluminum material toward the side of the high-purity aluminum material. For the concentration, the distance at which the concentration of the element contained becomes half of the concentration of the element contained in the low-purity aluminum material is taken as the diffusion distance.

(Thermal cycle test)

For the thermal cycle test, TSB-51 manufactured by ESPEC Co., Ltd. is used. For the test piece (power module with heat sink), the liquid phase (FLUORINERT) is performed 4000 times at -40°C for 5 minutes and at 150 ℃ 5 minutes thermal cycle.

Next, the bonding rate before and after the thermal cycle test was evaluated in the following manner. Also, visually evaluate the presence or absence of ceramic cracking after the thermal cycle test. The evaluation results are shown in Table 4.

(Joint rate)

The bonding rate between the metal layer and the heat sink is determined using an ultrasonic flaw detection device (FineSAT200 manufactured by Hitachi Power Solutions) and using the following formula. Here, the initial bonding area is assumed to be before bonding The joined area (37mm square). In the image obtained by binarizing the ultrasonic flaw detection image, the peeling is represented by a white portion in the joint portion. Therefore, the area of the white portion is taken as the peeling area.

(Bonding rate (%)) = {(initial bonding area)-(peeling area)}/(initial bonding area) × 100

In the conventional example 1, the bonding rate greatly decreased after the thermal cycle test. It is speculated that this is due to cracks in the solder layer due to thermal cycling.

In the conventional example 2, the bonding rate was greatly reduced after the thermal cycle test, and cracking was confirmed on the ceramic substrate.

In addition, in Comparative Example 1-3 in which the metal layer and the heat sink are composed of aluminum materials of the same purity, the metal layer and the heat sink cannot be joined under the above-described solid-phase diffusion conditions.

In contrast, in the examples of the present invention, either There was no significant increase in the post-bonding rate, and no ceramic cracking was confirmed, and the bonding reliability was excellent.

From the above, it can be confirmed that according to the present invention, a substrate for a power module with a heat sink can be manufactured that suppresses the occurrence of cracks at the bonding interface even in the case of thermal cycling under load.

[Industry availability]

According to the manufacturing method of the substrate for a power module with a heat sink according to the present invention, it is possible to reliably perform solid-phase diffusion bonding of the metal layer and the heat sink in a short time. In addition, since the heat sink and the metal layer are solid-phase diffusion-bonded, even in the case of load thermal cycling, there is no doubt that a crack or the like will occur at the bonding interface, and it is possible to obtain an excellent bonding reliability for thermal cycling. Substrate for power module of heat sink.

10‧‧‧ substrate for power module

11‧‧‧Ceramic substrate

12‧‧‧ circuit layer

13‧‧‧Metal layer

22‧‧‧Aluminum plate

23‧‧‧Aluminum plate

24‧‧‧Al-Si brazing material

30‧‧‧Substrate for power module with heat sink

31‧‧‧heat sink

Claims (5)

A method for manufacturing a substrate for a power module with a heat sink, which includes an insulating layer, a circuit layer formed on one side of the insulating layer, a metal layer formed on the other side of the insulating layer, and is disposed A method of manufacturing a substrate for a power module with a heat sink attached to a heat sink on a surface of the metal layer opposite to the insulating layer, a bonding surface of the metal layer with the heat sink, and a heat sink with the metal The bonding surface of the layer is composed of an aluminum material made of aluminum or aluminum alloy. Either of the aluminum material constituting the bonding surface of the metal layer and the aluminum material constituting the bonding surface of the heat sink is high in purity of aluminum A pure aluminum material, the other is a low-purity aluminum material with low purity of aluminum, the concentration difference between the high-purity aluminum material and the low-purity aluminum material other than Al is set to 1 atomic% or more, and the metal layer and The heat sink performs solid-phase diffusion bonding, and elements other than Al diffuse from the low-purity aluminum material side to the high-purity aluminum material side. The method for manufacturing a substrate for a power module with a heat sink according to claim 1, wherein the high-purity aluminum material and the low-purity aluminum material contain Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr One or two or more elements selected from the above are included as elements other than Al, and the total amount of elements other than Al in the high-purity aluminum material and the total amount of elements other than Al in the low-purity aluminum material are The difference in amount is 1 atomic% or more. The method for manufacturing a substrate for a power supply module with a heat sink according to claim 1, wherein the low-purity aluminum material contains a total of 1 atomic% or more of Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr One or more elements selected from among, and the content of Si is 15 atomic% or less, the content of Cu is 10 atomic% or less, the content of Mn is 2 atomic% or less, the content of Fe is 1 atomic% or less, Mg The content is 5 atomic% or less, the Zn content is 10 atomic% or less, the Ti content is 1 atomic% or less, and the Cr content is 1 atomic% or less. The method for manufacturing a substrate for a power supply module with a heat sink according to claim 2, wherein the low-purity aluminum material contains a total of 1 atomic% or more of Si, Cu, Mn, Fe, Mg, Zn, Ti, and Cr One or more elements selected from among, and the content of Si is 15 atomic% or less, the content of Cu is 10 atomic% or less, the content of Mn is 2 atomic% or less, the content of Fe is 1 atomic% or less, Mg The content is 5 atomic% or less, the Zn content is 10 atomic% or less, the Ti content is 1 atomic% or less, and the Cr content is 1 atomic% or less. The method for manufacturing a substrate for a power module with a heat sink according to any one of claims 1 to 4, wherein by laminating the metal layer and the heat sink, a load of 0.3 MPa or more is applied in the lamination direction , Under a load of 3.0 MPa or less, and maintained at a temperature above 90% of the solidus temperature (K) of the aforementioned low-purity aluminum material and at a holding temperature below the solidus temperature of the aforementioned low-purity aluminum material, for more than 1 hour, On the other hand, the metal layer and the heat sink are subjected to solid phase diffusion bonding.

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